What is the primary reason for using butter in the rubbing method for pastry?

The primary reason for using butter in the rubbing method for pastry is to create a flaky texture. When butter is incorporated into flour using this method, it is rubbed into the flour until the mixture resembles coarse crumbs. This process coats the flour particles with fat, which disrupts the formation of gluten. As a result, when the pastry is baked, the fat creates steam pockets, leading to a flakier and more tender texture.

While butter does contribute flavor and can enhance color in the final baked product, the main goal when using the rubbing method is to achieve that desirable flakiness. Additionally, butter does not serve to thicken the dough; rather, it adds richness and moisture, which are essential for the pastry's overall quality. Thus, the emphasis on texture explains why the use of butter in this context is crucial.